Thermochemical scarfing process



1965 J. DE VRIES ETAL 3, 7

THERMOCHEMI GAL S CARFING PROCES S Filed April 29, 1963 2 Sheets-Sheet 1 INVENTORS JOSEPH E. DeVRIES WILLIAM ALLMANG A T TORNEY Nov. 9, 1965 J. E. DE VRIES ETAL 3, ,367

THERMOCHEMICAL SGARFING PROCES S Filed April 29, 1963 2 Sheets-Sheet 2 r '26 Q R: =8 Q Q INVENTORS JOSEPH E. DeVRlES WILLIAM ALLMANG A T TORN United States Patent Office Patented Nov. 9, 1965 This application is in part a continuation of our copending application Serial No. 81,830, filed January 10, 1961, which is in part a continuation of our application Serial No. 756,690, filed August 22, 1958, and now abandoned.

This invention relates to thermochemical scarfing and more particularly, to the starting of a smooth flute on the surface of a body while such body is continuously moving at scarfing speed.

The main object of the invention is to obtain true flying starts of intermittent thermochemical scarfing at work speeds of at least 25 f.p.m. and preferably 60 to 120 f.p.m.

The invention provides a new method and apparatus for effecting starts at full machine-scarfing speed, such for example as that involved in the automatic selective scarfing process of application Serial No. 335,450, filed November 11, 1963.

According to the invention, there is provided a novel method of and means for making a true flying start of a thermochemical surface scarfing pass on a metal body intermediate the ends thereof while in continuous motion within the normal speed range of thermochemical scarfing of such body. This is accomplished by applying a stream of oxygen containing preheated burning adjuvant powder at an acute angle against said metal body at the point intermediate the ends thereof where the scarfing reaction is to be initiated to prepare the surface for starting. The starting oxygen stream carries said burning powder to such starting point which is thereby prepared for starting when the flow of oxygen in such stream is increased. Such flow is thereupon increased to a scarfing value and impinges the surface at the point which has previously received the starting oxygen stream and the combustible powder, starting the pass with a gradual increase in depth of the flute. The flow of oxygen in such stream prior to such start is less than the flow after such start, so that molten burning powder is deposited on such surface by such stream at such reduced oxygen flow before the oxygen flow is so increased to obtain such start. This assures good flute starts up to and including 90 feet per minute with either postmixed or premixed preheating flames.

The prior art was mainly concerned with making starts in thermochemically cutting (severing), a process different from scarfing. In cutting, the products of the reaction exhaust from the side opposite the cutting blowpipe. In scarfing, the products of the reaction exhaust from the same side as the scarfing unit. L1 cutting, the reaction is confined to a relatively narrow kerf. This confines the heat and minimizes preheat problems. In scarfing, the reaction is on an open surface. As a result, it is much more difiicult to retain heat. Therefore, making a cutting start and making a scarfing start involve different problems. The starts of our invention are full width starts that have a gradual increase in depth. This is more desirable than a narrow start that spreads.

Several methods of making so-called instantaneous starts on stationary workpieces are disclosed in the prior art. However, when such methods are applied to machine scarfing, they are found to be impractical.

Tests indicated that operationally it is much more difficult to make a start on a rapidly-moving workpiece than on a stationary one. When hand scarfing a stationary workpiece, the operator will inject adjuvant material into the preheat flame to bring such material to its ignition temperature. Simultaneously, the scarfing oxygen is turned on. The material burns in the scarfing oxygen and imparts heat to the cold body. This supplements the heat of the preheat flames and thereby, rapidly brings the workpiece to ignition temperature. This procedure is impractical for machine scarfing.

First of all, such procedure involves the discretionary powers of a skilled operator. If the operator sees his workpiece is not at ignition temperature, he will hesitate and continue preheating until the stationary workpiece is at ignition temperature. In a mechanized selective scarfing setup, where the scarfing process is but one step in the production processing of ferrous bodies, such a preheat dwell cannot be tolerated.

Starting on a moving workpiece must be consistent; that is, a start must be made every time without any dwell.

Secondly, in hand scarfing where the work is stationary, the operator has more control over the preheat material (powder or rod) and preheat flames. As a result, it is much simpler for him to make sure that the proper amount of adjuvant powder gets to the starting point. In mechanized operations, it was discovered that, when the powder and scarfing oxygen were turned on simultaneous-ly, the powder would blow away and never reach the moving workpiece and, a fortiori, never reach the starting zone.

Thus, a process was needed which would ensure proper preparation of a moving body for starting; that is, a method which would ensure the proper amount of adjuvant powder at the right spot at the right time.

In the method of the invention, adjuvant powder is injected into the preheat flames. Simultaneously, a controlled amount of starting oxygen is turned on. Powder is burned therein and conveyed to the exact point of starting on the moving workpiece intermediate the ends thereof. Such starting oxygen and adjuvant powder prepare the starting zone for the subsequent increase of the starting oxygen to scarfing oxygen flows.

This process is distinguishable from the prior art in that a controlled amount of oxygen is employed to get the adjuvant powder to burn properly and to convey such burning powder to the exact point of starting intermediate the ends of the workpiece, thereby preparing a moving workpiece for a subsequent flow of scarfing oxygen.

In actual operation, the starting oxygen is on during the entire scarfing cycle. The purpose is twofold. First, it eliminates a complex valving system which would be required to turn oxygen on and off, and second, when scarfing oxygen is turned on in one particular nozzle, the soft starting oxygen flow issuing from the non-operating nozzles on either side of the operating nozzle eliminates fins that may form along the edges of the scarfed pass. Thus, starting oxygen serves a second ancillary purpose. However, it is not essential to the present starting method that the starting oxygen be on all the time.

In the drawings:

FIGS. la to 10 are fragmentary perspective views of a billet in which a thermochemical metal removal operation involving the scarfing of a flute in the surface of a billet is being started, according to the prior art;

FIG. la is a fragmentary longitudinal-vertical sectional View of the billet taken on line 1d1d of FIG. 10, the apparatus being shown in side elevation;

FIGS. 2a to 20 are fragmentary perspective views of apparatus illustrating the invention;

FIG. 2d is a fragmentary view, partly in side elevation and partly in section, taken on line 2d-2d of FIG. 20; and

FIG. 3 is a fragmentary perspective view of apparatus illustrating the invention in operation.

Employing the best method of the prior art, flying starts could be made at speeds up to 25 f.p.m. In automatic selective scarfing, however, it is essential that true flying starts of the order of 60 f.p.m. or more be made. FIGS. 1a, 1b, 1c and 1d illustrate the type of flute obtainable with such heat prior method of making flying starts. It is to be noted that the flute is deep at C and key-hole shaped at the start B. With this type flute, when the steel is subsequently rolled, laminations are produced.

FIGS. 2a to 2d illustrate the type of flute that is obtainable with a properly made flying start, according to the invention. At the beginning, the scarf is shallow and slot-shaped on the top surface. Gradually, the depth D of the scarf increases to a maximum after an inch or two of travel. At the completion of the scar-fed defect, the depth gradually decreases until it is flush with the steel surface. This type of flute eliminates laminations when the steel is rolled in subsequent operations.

In the preferred method of operation, a cold steel billet W, FIG. 3, passes under a bank of individual scarfing nozzles N mounted in parallel so that the billet passes it in the proper relationship to permit scarfing. For simplicity of description, only one nozzle is shown in the drawing. Powder nozzle N is inclined at an angle of from 30 to 120 with the horizontal and is positioned 1 to 3 inches from the work. A scarfing nozzle N, located between such nozzle N and the work surface, is inclined at an angle of 25 to 40 with the horizontal and is spaced A to 1 /4 in. from the work. A stream of oxygen flows from nozzle N toward the work W, as long as such work is under the scarfing station.

In addition, preheat flames are turned on and remain on during the entire scarfing operation. A powder nozzle N is provided for each scarfing nozzle N. Valve V is opened, permitting starting oxygen 1200 c.f.h. to 2000 c.f.h. to flow. When a defect approaches nozzle N a circuit is closed to timer T which energizes a solenoid S thereby opening the valve V and initiating the flow of powder which is injected into the preheat flame and oxygen stream. A stream of burning powder is thus laid down on the work at a point ahead of the scarfing nozzle N.

Then, through timer T the solenoid S is energized and valve V is opened, increasing oxygen stream flow to a sca-rfing value. The scarfing oxygen stream impinges the work at the point which has previously received the burning powder and starting oxygen stream, thereby initiating the flute-making scarfing reaction. For carbon steel applications, the powder flow is shut off as soon as the reaction is started as it is not needed to sustain the reaction. The scarfing oxygen flow is kept at the amount required for scarfing the full length of the defect. At the end of the defect, the oxygen flow is reduced at a controlled rate to permit it to burn the 4 molten metal that is flowing ahead of the scarfing pass and thus eliminate any excess metal that is removed from the flute and is flowing on the surface.

Employing the method of the invention, the combustible powder is injected into the preheat flame to bring the powder to its ignition temperature. The oxygen jet ignites the powder and carries it to the region of the metal body where the start is to be made. As a result, burning powder is laid down ahead of the scarfing station and before the starting oxygen jet is increased to a scarfing oxygen flow. As the powder impinges the work, the starting oxygen jet is increased to a scarfing oxygen flow and the reaction is initiated at the point which has been preheated by the combusted prelaid powder. This speed may be increased to perhaps 120 f.p.m. However, the work done so far represents substantial advancement in the art of making flying starts so that it is now possible to start at f.p.m. whereas, using the methods of the prior art, we were limited to maximum speeds of 25 f.p.m.

In summary, according to the present invention: (1) consistently good starts are obtainable, without any dwell for preheat, at speeds of 90 f.p.m.; (2) two distinct oxygen flows are employed; (3) a quantity of adjuvant powder, fed externally of the scarfing nozzle, is injected into the preheat flame and is carried by the preheat and the starting oxygen stream to a service portion of the metal body to raise the metal to its ignition temperature; (4) the starting oxygen flow is subsequently increased to a scarfing oxygen flow, thereby initiating the scarfing reaction on the portion of metal which has received the burning adjuvant powder.

With a premixed nozzle, the preheat flames exit from a set of flame ports surrounding the oxygen orifice through which the starting and scarfing oxygen exits. Practically speaking, it was found that the valving system becomes quite complex when a number of nozzles are employed. As a result, in recent tests the preheat flame, as well as the starting oxygen, were turned on and left on. For each start, the powder was injected into the preheat flame and carried by the starting oxygen to the starting zone. This eliminates a valve in the timing circuit for the starting oxygen.

Referring to FIG. 3, the valve 5 is turned on and off before and after scarfing each billet.

In a post-mixed nozzle all the oxygen (preheat, starting and scarfing) exits through the same orifice. In operation then, the starting oxygen stream is turned on and left on (starting oxygen in this case includes both starting oxygen and preheat oxygen). When a start is to be made, the powder is turned on and injected into the post-mixed preheat flame, which carries the burning powder to the scarfing zone; subsequently, the scarfing oxygen is turned on.

Referring to FIG. 3, when a post-mixed nozzle is employed, starting oxygen and preheat oxygen come on through valve V as explained above. Valve 1 is used for scarfing oxygen.

The powder blend employed in the process of the invention preferably is a 15% aluminum, 85% iron blend. A iron powder may also be used successfully, but at a lower scarfing speed.

Below are the data obtained during recent tests:

1. POST-MIXED NOZZLE A. Scarfing conditions Maximum variation Nozzle SL-30 1 post-mixed Angle, 30 deg. 25-40 deg. Height %1% inch.

See Patent No. 2,353,31S-The preheat orifices are an proximately .0635" in diameter, the oxygen slot is about .562 long and .140" wide.

1 See Patent No. 2,7 54,234 entitled Thermochemical Metal Removal. The powder orifices are approximately =34, long and .040 Wide, area 0.03.

C. Gas pressure settings and flow rates Optimum, Maximum c.t.h. V ariation,

c.f,h.

Starting Oxygen, to 20 p.s.i 2,000 1, 260-2, 000 scarfing Oxygen, 40 psi. 2, 800 Acetylene. 4 p.s.i 125 100-200 Powder Air 200 200300 D. Timing Scarfing oxygen valve 1 was timed to open 0.3 sec. after the powder and starting oxygen was turned on.

2. PREMIXED NOZZLE A. Scarfing conditions Nozzle SL30 premixed Angle 30 deg. Height 1 /24 4 in.

B. Powder conditions Optimum Maximum Variation Nozzle Atlas Type.-. Angle, deg. 85 to 95 75400 Height, in 2% to 2% 2-3 Flow Rate,1b./niin./noz.!stsrt 6 to 8 3-8 C. Gas pressure settings and flow rates Optimum, Maximum c.f.h. Variation,

e.f.h.

Preheat Oxygen, 10 to 14 p.s.i 60-90 Starting Oxygen 5 to s i 1, 200-2, 000 scarfing Oxygen, 40 p s Acetylene, 9 to 12 p.s. 704 5 Powder Air oo-s00 D. Timing Scarflng oxygen valve 1 is timed to open 0.3 sec. after the powder and starting oxygen are turned on.

In the premixed nozzle, the preheat flame can vary 1n the range from slightly carburizing to slightly oxidizing. The above data merely cites the conditions of these particular tests.

Additionally, the powder air flow is critical when speaking of a particular powder flow rate. Powder air flow should be of such a nature as to convey the powder into the preheat flame at the correct velocity. If the velocity is too low, the powder will blow away. If it is too high, the powder may blow straight through the preheat flame with the result that the powder never gets to the starting zone.

What is claimed is:

1. Process of starting a thermochemical scarfing pass to cut a smooth flute in the surface of a ferrous metal body moving at a constant selected speed within the normal speed range of thermochemical scarfing of such body, which comprises applying a stream of oxygen-containing preheated burning powder at an acute angle against such moving surface to prepare the latter for starting when the flow of oxygen in such stream is increased, and increasing such flow of oxygen to the scarfing value to start the thermochemical pass with a gradual increase in width and depth of the flute without any change in the movement of the body at such selected scarfing speed.

2. Process of flying starting a thermochemical desurfacing operation without any dwell which comprises continuously moving a body to be desurfaced past a desurfacing station provided with means for applying to such body a stream of adjuvant powder, a preheating flame and a stream of oxygen; and, while such body is moving without interruption by such station, applying such streams of powder, flame and oxygen simultaneously against a surface portion of the body at an acute included angle thereto; initiating a thermochemical reaction with the powder on such body and then substantially increasing the flow of such oxygen stream to initiate a desurfacing operation with the material of the surface of such body adjacent such burning powder.

3. Process of thermochemical scarfing relatively cold bodies of steel, which comprises continuously moving each body at a speed of at least 25 feet per minute along a path adjacent a scarfing station and, as a surface defect on such moving body approaches said station, applying to such moving surface at a point directly in front of the leading edge of said defect a plurality of preheating flames, a starting oxygen stream and a stream of adjuvant powder so that at least a portion of the powder enters the preheating flames and such starting oxygen stream just before the latter hits such point in front of the leading edge of the defect to be removed; and, while the body continues its movement along such path, increasing the flow of such starting oxygen stream to a scarfing value, thereby starting a flute-forming thermochemical removal operation only in the area of such point on said moving surface without any interruption in the movement of the body.

4. Selective thermochemical scarfing which comprises continuously moving a relatively cold body of steel along a predetermined path adjacent a station provided with a thermochemical scarfing device which includes an oxygen nozzle arranged at an acute angle to the surface of such body, and a powder nozzle disposed in front of said oxygen nozzle, simultaneously preheating and applying a burst of adjuvant powder from said powder nozzle while discharging a stream of starting oxygen from said oxygen nozzle against such moving body surface, and then increasing the flow of such starting oxygen stream to a scarfing value to start a scarfing cut on such moving surface for the purpose of removing metal in the area of a defect, and continuing such preheating and scarfing oxygen stream to thermochemically remove such defect.

5. A thermochemical scarfing process which comprises continuously moving a relatively cold steel body along a predetermined path adjacent a station provided with a thermochemical scarfing device which includes a main nozzle inclined at an acute angle toward the surface of such body and an auxiliary nozzle mounted in front of such main nozzle, discharging an oxygen stream from such main nozzle at a relatively low starting flow toward such body surface as it moves by said station, and simultaneously discharging from said m-ain nozzle an annular row of oxy-fuel gas-preheating flames that surround such starting oxygen stream and also are directed toward such surface; and discharging a burst of adjuvant powder from said auxiliary nozzle toward said surface as a surface defeet to be removed from such body approaches said main nozzle and at about the same time increasing the flow of such starting oxygen to produce a scarfing oxygen stream.

5. Method of thermochemically scarfing steel bodies which comprises continuously moving the body to be so scarfed at a speed of 25 to feet per minute through a station provided with a scarfing device which includes means for automatically smoothly starting, continuing and stopping a flute-producing thermochemical metal-removal operation of restricted width on the surface of such moving body without any interruption in such movement, applying a stream of starting oxygen with adjuvant powder from said scarfing device, and immediately thereafter applying a scarfing oxygen stream having a greater flow rate than said flow of starting oxygen to the surface of such moving body to start the scarfing reaction without any dwell in the movement of such body.

'7. Process of starting a thermochemical scarfing pass to cut a smooth flute in the surface of a ferrous metal body moving at a constant selected speed within the normal speed range of thermochemical scarfing of such body, which comprises applying preheat flames to said body, applying to said preheated body a stream of starting oxygen of the order of 1200 to 2000 c.f.b., applying a stream of gas borne powder into said preheat flames to lay down a stream of burning powder on the work to prepare the latter for starting when the flow of oxygen in such stream is increased, and increasing such flow to the scarfing value to start the thermochemical pass with a gradual increase in width and depth of the flute without any change in the movement of the body at such selected scarfing speed, so that molten burning powder is deposited on such surface at such reduced oxygen flow before the oxygen flow is so increased to obtain such start.

8. Process of flying starting a thermochemical desurfacing operation without any dwell which comprises continuously moving a body to be desurfaced past a desurfacing station, and at said station applying preheat flames to said moving body, applying to said preheated body a stream of starting oxygen of the order of 1200 to 2000 c.f.h., applying a a stream of gas borne powder into said preheat flames to lay down a stream of burning powder on the work, and while such body is moving without interruption by such station, applying such streams of powder, flame and oxygen simultaneously against a surface portion of the body at an acute included angle thereto thereby initiating a thermochemical reaction with the powder on such body; and after an interval of the order of 0.3 second from the start of the powder and starting oxygen substantially increasing the flow of such oxygen stream to the order of 2800 cubic feet per hour under a pressure of the order of 40 pounds per square inch to initiate a desurfacing operation with the material of the surface of such body adjacent such burning powder.

9. Process of thermochemical scarfing relatively cold bodies of steel, which comprises continuously moving each body at a speed of at least 25 feet per minute along a path adjacent a scarfing station and, as a surface defect on such moving body approaches said station, applying to such moving surface at a point directly in front of the leading edge of said defect a plurality of preheating flames, a starting oxygen stream at a flow of the order of 1200 to 2000 cubic feet per hour under from to 20 pounds per square inch pressure, and a stream of adjuvant powder of the order of from three to eight pounds per minute so that at least a portion of the powder enters the preheating flames and such starting oxygen stream just before the latter hits such point in front of the leading edge of the defect to be removed; and, while the body continues its movement along such path, increasing the flow of such starting oxygen stream to a scarfing oxygen value, thereby starting a flute-forming thermochemical removal operation only in the area of such defect on said moving surface without any interruption in the movement of the body.

10. Selective thermochemical scarfing which comprises continuously moving a relatively cold body of steel along a predetermined path adjacent a station provided with a thermochemical scarfing device which includes an oxygen nozzle arranged at an acute angle to the surface of such body and a powder nozzle having an orifice area of the order of 0.030 inch and disposed in front of said oxygen nozzle, simultaneously preheating and applying a burst of adjuvant powder from six to eight pounds per minute from said powder nozzle while discharging a stream of starting oxygen at a flow of the order of 1200 to 2000 cubic feet per hour under from 5 to 20 pounds per square inch pressure from said oxygen nozzle against such moving body surface, and then increasing the flow of such starting oxygen stream to a scarfing oxygen value to start a scarfing cut on such moving surface for the purpose of removing metal in the area of a defect, and continuing such preheating and scarfing oxygen steam to thermochemically remove such defect.

11. A thermochemical scarfing process which comprises continuously moving a relatively cold steel body along a predetermined path adjacent a station provided with a thermochemical scarfing device which includes a main nozzle having an orifice of the order of .562 inch long and .140 inch wide and inclined at an acute angle toward the surface of such body and an auxiliary nozzle mounted in front of such main nozzle, discharging an oxygen stream from such main nozzle at a relatively low starting flow of 1200 .to 2000 cubic feet per hour under from 5 to 20 pounds per square inch pressure toward such body surface as it moves by said station, and simultaneously discharging from said main nozzle an annular row of oxyfuel gas-preheating flames that surround such starting oxygen stream and also are directed toward such surface; and discharging a burst of adjuvant powder of from six to eight pounds per minute from said auxiliary nozzle toward said surface as a surface defect to be removed from such body approaches said main nozzle and at about the same time increasing the flow of such starting oxygen to of the order of 2800 cubic feet per hour under a pressure of the order of 40 pounds per square inch to produce a scarfing oxygen stream.

12. Method of thermochemically scarfing steel bodies which comprises continuously moving the body to be so scarfed at a speed of 25 to feet per minute through a station provided with a scarfing device which includes means for automatically smoothly starting, continuing and stopping a flute-producing thermochemical metalremoval operation of restricted width on the surface of such moving body without any interruption in such movement, applying a stream of starting oxygen at a flow of the order of 1200 to 2000 cubic feet per hour under from 5 to 20 pounds per square inch pressure and a stream of adjuvant powder of the order of from six to eight pounds per minute to the surface of such moving body immediately before a scarfing oxygen stream of the order of 2800 cubic feet per hour under a pressure of the order of 40 pounds per square inch is applied to the surface of such moving body to start the scarfing reaction without any dwell in the movement of such body.

13. Process of starting a thermochemical scarfing pass to cut a smooth flute in the surface of a ferrous metal body intermediate the ends thereof while moving at a constant selected speed within the normal speed range of thermochemical scarfing of such body, which comprises applying a stream of oxygen-containing preheated burning powder at a flow of the order of 1200 to 2000 cubic feet per hour under from 5 to 20 pounds per square inch pressure at an acute angle against such moving surface to deposit molten burning powder on such moving surface and thereby prepare it for starting a thermochemical scarfing reaction thereon and increasing such flow to the scarfing value of the order of 2800 cubic feet per hour under a pressure of the order of 40 pounds per square inch to start the thermochemical pass with a gradual increase in width and depth of the flute without any change in the movement of the body at such selected scarfing speed, and shutting off the flow of said powder.

14. Process of starting a thermochemical scarfing pass to cut a smooth flute in the surface of a ferrous metal body moving at a constant selected speed within the normal speed range of thermochemical scarfing of such body, which comprises directing preheat flames toward said moving body, and when the body reaches scarfing position directing a stream of starting oxygen at materially less than scarfing value from an orifice through said preheat flames toward said body to form an continual stream of preheat flames and starting oxygen, directing into said combined stream a stream of gas borne powder to intersect the same at a sufilcient distance beyond said orifice before it reaches the body to heat the powder to kindling temperature but far enough above the body to prevent precombustion thereof and thereby to lay down a stream of molten burning powder on said body to prepare the latter for starting when the flow of oxygen is increased, and increasing such flow through said orifice to scarfing value to start the thermochemical pass.

References Cited by the Examiner UNITED STATES PATENTS 2,622,048 12/52 Moesinger 26623 2,873,224 2/59 Thompson et al 148-95 10 3,033,133 5/62 Keller et a1 110-22 DAVID L. RECK, Primary Examiner. 

1. PROCESS OF STARTING A THERMOCHEMICAL SCARFING PASS TO CUT A SMOOTH FLUTE IN THE SURFACE OF A FERROUS METAL BODY MOVING AT A CONSTANT SELECTED SPEED WITHIN THE NORMAL SPEED RANGE OF THERMOCHEMICAL SCARFING OF SUCH BODY, WHICH COMPRISES APPLYING A STREAM OF OXYGEN-CONTAINING PREHEATED BURNING POWDER AT AN ACUTE ANGLE AGAINST SUCH MOVING SURFACE TO PREPARE THE LATTER FOR STARTING WHEN THE FLOW OF OXYGEN TO THE SCARFING VALUE TO START THE THERMOCHEMICAL PASS WITH A GRADUAL INCRASE IN WIDTH AND DEPTH OF THE FLUTE WITHOUT ANY CHANGE IN THE MOVEMENT OF THE BODY AT SUCH SELECTED SCARFING SPEED. 